A conventional clip attachment structure for a writing instrument is known, in which the back end side of a clip is attached and fixed to the back end side of a shaft tube by a tail crown such that only the clip is exposed outside of the shaft tube in terms of aesthetics (see, for example, JP Patent Application Publication 2008-194927).
With regard to the specific construction of a clip attachment structure for a writing instrument described in JP Patent Application Publication 2008-194927 by the applicant, a notch for fitting a base of a clip therein is formed at the back end of a shaft tube, and a window-shaped opening that opens in front of the notch (hereinafter referred to as a middle opening) is provided at a middle part of the shaft tube. In the clip to be attached to the shaft tube, hook-like engaging pieces are formed on both sides of the back end of the clip and on both sides near a middle part of the clip, i.e., at a total of four locations. When the clip is attached, the engaging pieces near the middle part of the clip catch on and engage the front end edge of the middle opening of the shaft tube, and at the same time the engaging pieces at the back end of the clip catch on and engage a notch edge of the notch at the back end of the shaft tube. While in this state, an insertion part of a tail crown is inserted into the back end of the shaft tube, and an engagement recess formed in the insertion part engages an engagement protrusion formed near the notch of the shaft tube, thereby achieving a construction in which the back end of the clip is sandwiched and fixed between a collar (flange) formed at the back end of the tail crown and the notch of the shaft tube.
According to such a clip attachment structure for the writing instrument of the above-noted patent document, the advantage is that the base of the clip may be rigidly attached to the shaft tube with a relatively easy operation, and only the clip is exposed outside of the shaft tube to achieve aesthetics.